The present invention relates to modified reinforced epoxy tape backings.
The present invention relates to silicone modified reinforced epoxy tape backings.
The present invention more particularly relates to a tape backing assembly comprising a silicone modified epoxy coated over a polyamide or polyester non-woven fabric material.
The present invention also relates to modified epoxy tape backings particularly useful for electrical tapes.
In applications where electrical tapes are required, the following are some of the important characteristics of such a tape: thermal stability, high dielectric strength, good electrical insulation properties, water resistance, and flame retardancy.
The conventional electrical tapes on the market with epoxy backings are designed for use at temperatures of up to about 130.degree. C. The tape of the present invention is designed to perform satisfactorily at temperatures of up to about 160.degree. C.
The tape of the present invention additionally exhibits dielectric strength values ranging from about 7.2 KV to about 8.7 KV. The conventional epoxy backed tapes, on the other hand, exhibit dielectric strength values in the range of from about 5.0 KV to about 6.5 KV.
The incorporation of silicone in the epoxy tape backing of the present invention results in the formation of an increased hydrophobicity of the film. This gives rise to a tape backing having improved water and chemical resistance characteristics.
Prior art embodiments have required that a release coating be applied to the tape during manufacture, in order to permit satisfactory unwinding of the tape during its use. Alternatively, the prior art embodiments may use a release liner in either the manufacture and/or use of the tape in order to permit satisfactory unwinding.
On the other hand, the tape backings of the present invention offer the important advantages of not requiring either a release coating or release liner in application.
It should be noted that the incorporation of the silicone in the epoxy resin results in enhanced chemical resistance as well as a decreased surface tension, which imparts the desired antiblocking characteristics to the tape backing of the present invention.
U.S. Pat. No. 3,154,597 describes polysiloxane modified epoxide resins. However, the '597 patent utilizes a reaction with a siloxy group, whereas the present invention utilizes a hydroxyl reaction with a carbinol group. The silicone reactant in the '597 patent is a product similar to Dow Corning's "Sylkyd 50".TM., which is essentially a methoxy terminated siloxane.
It should be noted that unlike other siliconized epoxy resins of the prior art, the present invention is based on the reaction of the epoxy resin with the organic portion of a siloxane copolymer. The reaction of the epoxy with carbinol proceeds more rapidly and with greater facility than reaction with a silanol group.